Information Systems Group

Hermit OWL Reasoner

The New Kid on the OWL Block

Overview

HermiT is reasoner for ontologies written using the Web Ontology Language (OWL). Given an OWL file, HermiT can determine whether or not the ontology is consistent, identify subsumption relationships between classes, and much more.

HermiT is the first publicly-available OWL reasoner based on a novel “hypertableau” calculus which provides much more efficient reasoning than any previously-known algorithm. Ontologies which previously required minutes or hours to classify can often by classified in seconds by HermiT, and HermiT is the first reasoner able to classify a number of ontologies which had previously proven too complex for any available system to handle.

HermiT uses direct semantics and passes all OWL 2 conformance tests for direct semantics reasoners.

We have now released HermiT 1.2 under the GNU Lesser General Public License (LGPL) (before HermiT was GPL). The release should be compatible with Java 1.5. HermiT 1.2 uses the OWL API 3.0.0. The OWLReasoner interface of the OWL API has been significantly redesigned and we implement all methods of the new interface. We do not provide deprecated methods for the now obsolete old interface. The release contains minor bug fixes, improved memory management, and a new blocking strategy, called core blocking, that can significantly reduce the amount of memory required by HermiT. This new strategy is used as a default for ontologies with nominals. For other ontologies HermiT uses a blocking cache that makes classification much faster, but is not yet compatible with the new blocking strategy. The Eclipse project now also contains examples for common uses of HermiT from Java.

Since version 1.1, HermiT can handle DL Safe rules and the rules can directly be added to the input ontology in functional style or other OWL syntaxes supported by the OWL API (see A Syntax for Rules in OWL 2).

HermiT is open-source and released under LGPL. All components and source code is included in the project folder of the release.